1. Field of the Invention
The invention relates to a hearing protection earpiece comprising a customized shell.
2. Description of Related Art
Customized earpieces are earpieces comprising a hard shell which has an outer surface individually shaped according to the measured inner shape of the user's outer ear and ear canal. Such shape measurement can be carried out, for example, by direct laser scanning of the user's ear or by forming an impression which then is laser-scanned. The customized hard shell may be produced by an additive process, such as layer-by-layer laser sintering of a powder material. Customized earpieces of this type are described, for example, in International Patent Application Publication WO 02/071794 A1, and U.S. Pat. Nos. 6,766,878 B2 and 6,533,062 B1.
In general, hearing protection devices may be passive or active, i.e., dynamic. Passive hearing protection earpieces typically comprise a passive acoustic filter which allows for some frequency adjustment of the sound attenuation. Dynamic hearing protection earpieces comprise a microphone for capturing audio signals from ambient sound and a loudspeaker for emitting sound into the ear canal; in addition, an audio signal processing unit for processing the audio signals captured by the microphone and for supplying processed audio signals to the loudspeaker is provided, either as part of the earpiece or as a separate body-worn unit. With active hearing protection devices level-dependent attenuation of sound is achieved, so that protection from high noise levels can be realized while at low noise levels perception of useful sound can be perceived without the need to remove the hearing protection device. Examples of active hearing protection earpieces are found, for example, in European Patent Application EP 1 674 061 A1, and International Patent Application Publications WO 2007/082579 A2, WO 2009/050306 A2 and WO 2010/133701 A2.
One problem encountered with hearing protection devices is that the ability of the user to localize a sound source is significantly deteriorated when wearing the hearing protection device. This applies in particular to the localization in elevation and to front-back discrimination. However, in particular for military or police applications or in certain industrial working applications, an accurate localization of sound sources is of major importance to the user of the hearing protection device. In critical situations, this may result in the problem that the user decides to not wear the hearing protection device.
U.S. Pat. No. 4,677,678 relates to a hearing protection earmuff comprising an outer microphone, an audio signal processing unit including an automatic gain control (AGC) circuit and a loudspeaker. Since such arrangement acoustically by-passes the pinna, localization information is partially lost or significantly modified.
International Patent Application Publication WO 2011/033136 A2 relates to a dynamic hearing protection device which is completely worn in the ear canal, whereby localization information may be preserved to a high extent.
EP 1 322 268 B1 relates to a dynamic hearing protection earplug comprising both an outer microphone for capturing ambient sound and an inner microphone oriented towards the ear canal for capturing the user's voice. The earplug is designed to fill part of the concha and may be combined with an audio communication device for enabling wireless communication with other persons.
Dynamic hearing protection earpieces of the full concha type having a customized shell filling the concha are available under the product designation “Serenity” from Phonak Communications AG, Murten, Switzerland.
U.S. Pat. Nos. 5,742,689 and 6,002,775, and International Patent Application Publications WO 2010/092307 A1, WO 2007/123788 A2 and WO 2010/048157 A1 describe various methods of combining multiple audio sources into two stereo channels supplied to headphones/earphones by using head-related transfer functions (HRTF), with the positions of the sources being known.
U.S. Patent Application Publication 2011/0130786 A1 relates to a device for treating headache, which is designed as an intra-aural device comprising a rigid shell which is provided with a scalloped indenture which is open towards ambience.